Browsing by Author "Cheng, T. C."

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Improved field emission properties of thiolated multi-wall carbon nanotubes on a flexible carbon cloth substrate
(2007-10-03)
Chuang, F. T.
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Chen, P. Y.
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Cheng, T. C.
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Chien, C. H.
;
Li, B. J.
In this paper we report the observation of enhanced field emission properties from thiolated multi-wall carbon nanotubes ( MWCNTs) produced by a simple and effective two- step chemical surface modification technique. This technique implements carboxylation and thiolation on the MWCNTs synthesized by microwave plasma chemical vapor deposition ( MPCVD) on the flexible carbon cloth substrate. The resulting thiolated MWCNTs were found to have a very low threshold field value of 1.25 V mu m(-1) and a rather high field enhancement factor of 1.93 x 10(4), which are crucial for applications in versatile vacuum microelectronics.
Nanomanipulation measurement and PIC simulation of field-emission properties from a single crystallized silicon nano-emitter
(2007-06-06)
Cheng, T. C.
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Hsu, K. H.
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Chen, P. Y.
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Huang, W. J.
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Wu, J. S.
The field-emission characteristics of a single silicon nano-emitter were investigated by means of experiments and simulation models. The emitter array was fabricated by dry etching using an inductively coupled plasma (ICP) through a three-step process. A novel experimental technique was developed to precisely measure the field-emission current from a single silicon emitter. Accompanying these measurements, a parallelized three-dimensional particle-in-cell (PIC) code, in which the Fowler - Nordheim emission law was implemented at the emitter surface, was employed to simulate the emission current both with and without taking into account the space charge effect. Results show that the simulated I - V relationship when considering the space - charge effect was in excellent agreement with the actual measurements. Noticeably, the predicted turn-on voltage was found to be within only 9.3% of the experimental data. In addition, both the predicted and experimental data demonstrated a consistent single linear slope in the FN plot, which indicates that the field emission from a single silicon tip is a barrier-tunnelling, quantum mechanical process.
Saturated flow boiling heat transfer and associated bubble characteristics of FC-72 on a heated micro-pin-finned silicon chip
(2007-09-01)
Lie, Y. M.
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Ke, J. H.
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Chang, W. R.
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Cheng, T. C.
;
Lin, T. F.
An experiment is carried out here to investigate flow boiling heat transfer and associated bubble characteristics of FC-72 on a heated micro-pin-finned silicon chip flush-mounted in the bottom of a horizontal rectangular channel. Besides, three different micro-structures of the chip surface are examined, namely, the smooth, pin-finned 200 and pin-finned 100 surfaces. The pin-finned 200 and 100 surfaces, respectively, contain micro-pin-fins of size 200 mu m x 200 mu m x 70 mu m (width x length x height) and 100 mu m x 100 mu m x 70 mu m. The pitch of the fins is equal to the fin width for both surfaces. The effects of the FC-72 mass flux, imposed heat flux, and surface microstructures of the silicon chip on the FC-72 saturated flow boiling characteristics are examined in detail. The experimental data show that an increase in the FC-72 mass flux causes a delay in the boiling incipience. However, the flow boiling heat transfer coefficient is not affected by the coolant mass flux. But adding the micro-pin-fin structures to the chip surfaces can effectively enhance the single-phase convection and flow boiling heat transfer. Moreover, the mean bubble departure diameter and active nucleation site density are reduced for a rise in the FC-72 mass flux. A higher coolant mass flux results in a higher mean bubble departure frequency. Furthermore, larger bubble departure diameter, higher bubble departure frequency, and higher active nucleation site density are observed at a higher imposed heat flux. We also note that adding the micro-pin-fins to the chips decrease the bubble departure diameter and increase the bubble departure frequency. However, the departing bubbles are larger for the pin-finned 100 surface than the pin-finned 200 surface but the bubble departure frequency exhibits an opposite trend. Finally, empirical equations to correlate the present data for the FC-72 single-phase liquid convection and saturated flow boiling heat transfer coefficients and for the bubble characteristics are provided. (c) 2007 Elsevier Ltd. All rights reserved.